Why were the 10 Amendments added to the Constitution?

The first ten amendments to the United States Constitution are called the Bill of Rights, and they were written by James Madison. The Bill of Rights were added to the Constitution to assuage the fears of Anti-Federalists like former Virginia governor Patrick Henry who were worried that the Constitution gave the government too much power. The American Revolution had been a stand against King George and the British government's oppressive policies; the Anti-Federalists didn't want America to adopt a Constitution that would create a ruling class exactly like the one they'd just fought to free themselves from in the Revolutionary War.
The Bill of Rights puts limits on what the federal government can and can't do, and it protects individual rights, like freedom of speech and religion (Amendment I), the right to bear arms (Amendment II), and the right to a trial by jury (Amendment VII). These first ten amendments were modeled after the Virginia Declaration of Rights, which was composed by George Mason, who, when all was said and done, didn't believe the Bill of Rights did enough to protect individual rights.
https://billofrightsinstitute.org/founding-documents/bill-of-rights/